The present invention relates to soot blowers for dislodging ash accumulations from the convection surfaces of heat exchangers, and more particularly, a soot blower adapted for cleaning the convection surfaces of heat exchangers disposed in a coal gasifier by using the combustible product fuel gas as the soot blowing fluid.
Soot blowers have been used for years to clean ash deposits from the convection surfaces of heat exchangers of coal-fired steam generators. Typically, these prior art soot blowers comprise an elongated lance operatively associated with a motor so that the lance may be translated for long distances into the furnace of the steam generator so as to reach the heat exchange surface disposed therein. A cleaning fluid passes into the lance at a location outside of the furnace, traverses the lance, and is discharged through holes in the discharge end of the lance or through a nozzle attached thereto.
A number of cleaning fluids, such as air, steam, water, or flue gas, have been utilized in these conventional soot blowers. These fluids have proven quite satisfactory for use in dislodging ash from heat exchange tube bundles disposed in coal-fired furnaces. However, a significant problem exists when these aforementioned cleaning fluids are used for dislodging ash deposits from the heat exchange surface of tube bundles disposed in a coal gasifier. The problem being that these fluids all tend to dilute the combustible product fuel gas formed in the coal gasifier thereby lowering its heating value.
One solution to this problem is disclosed and claimed in my co-pending application Ser. No. 175,999, filed Aug. 7, 1980. As proposed therein, combustible product fuel gas is used as the blowing medium. In this way, the fuel gas formed in the coal gasifier is not diluted by the soot blowing fluid used to clean ash deposits from the heat exchange surface disposed within the gasifier.
However, the conventional prior art soot blowers are not satisfactory for use with combustible product fuel gas as the soot blowing medium. The conventional soot blowers of the prior art tend to suffer from severe leakage around various seals which must be incorporated into their design in order to permit the lance to be translated into and out of the gasifier in order to obtain access to the heat exchange surface disposed therein. If air or steam or flue gas are used as the soot blowing medium, such leakage should not create any serious problems. However, when combustible product fuel gas is used, such leakage presents the serious problem that an explosion could very well occur due to the combustible nature of the soot blowing fluid.